Heathkit HR-1680 bulbs

[Garey Barrell]

Good point.

According to the schematic, the unreg is +25V !!  Regulated is 13.8 V which
drives the bulbs and the rest of the receiver.  There is a 3/4A
(hopefully!) fuse at the output of the regulator, but if there is 25V on
the rest of the receiver .....

The regulator pass transistor is on a heatsink at the corner of the
Audio/Regulator board, and the fuse is right next to it on the board.  You
should have 25V on the transistor tab, and 13.6 on the fuse.

Most likely someone has put some "easier to find" 12V bulbs, (or perhaps
even 6-8V #47s!) in there.  47's last a long time at 12V.  Look what they
had to put up with in the old AC-DC sets until the 35Z5 filament heated up! :-)

73, Garey - K4OAH
Atlanta


At 02:57 PM 8/22/2002, Gerald C. Lemay wrote:
>Before you go any further, measure the voltage at the bulb sockets to make
>sure it is not over voltage. I don't have the manual right now but +V
>should be in the vicinity of 12 to 13 volts. Others may correct me on this.
>I would also expect to see anywhere from 16 to 18 VDC at the input to the
>regulator (based on design experience). Since both lamps are burned out and
>it appears that a lot of extra heat was generated next to the plastic
>parts, that might be evidence of a blown regulator which is passing on the
>full voltage appearing at the regulator input. Unfortunately the BAMA
>website does not have the manual but there are other sources on the web
>where you may be able to purchase a manual.
>
> > First of all, I'm new to this list and am glad to be part of it.  Right
> > now, I'm trying to rescue a HR-1680.  The front panel bulbs are burned
> > out, and since the plastic shows signs of heat damage, I half suspect
> > that those installed are the wrong ones.  (It was a common practice to
> > replace the original ones with brighter ones, which always led to
> > "browned" plastic.)  Could anyone suggest the correct bulb?  I don't
> > have a manual/schematic available.  Thanks in advance.
> >
> > Fred Wittman

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